We should not accept the premise that the pun is the lowest form of humor, because if we do, we miss the great pleasure of searching for forms even lower.

Benny Hill, from all appearances a fearlessly tasteless explorer in this well-trampled realm, makes the quest just short of uproarious in "The Benny Hull Show," premiering tonight at 11:30 and henceforth to be seen Tuesday through Fridays in that time alot on Channel 20, Washington's worst television station.

"How potent cheap music is," Noel Coward noted. And how funny old jokes are if they are tossed about with the kind of zip that Hill, a veteran British comic, brings to this program, 50 half-hours that have been edited for American viewing from the past 10 years of Hill's program on British TV. Essentially, Hill's is old-sytled burlesque comedy cranked up to 78 rpm for television, as speedy as it is racy. Hill does the kind of humor that people were hoping Milton Berle would revive when he recently hosted "Saturday Night Live;" broad, raucous, slapstick. There are also sight gags worthy of Ernie Kovacs.

But all of it is marked by a bawdiness and slap-happy vulgarity unlike anything on American television, even the American shows like "Three's Company" that were adapted from British hits ("Man About the House," in that case).

On a program such as this, and few are girl in a bikini can pop up literally anywhere; the important thing is that whe will. When Hill, as a bumblesome Australian cowboy called "Digger Blue," playfully puts a hand on a woman's breast, there is a "beep" noise on the soundtrack. "With this aword, I dub thee knight," says the queen, gingerly slicing off his ear.

The double-entendre flows like Schweppes and is just as curiously refreshing, especially during "Deep in My Heart," a wide-screen movie which, when shown on television, turns into "Deep In My Ear." During the closing sketch on the premiere-a fast-motion taped pantomine, like the opening-they even blow up what used to be known as an "outhouse."

Hill, who looks like Rod Steiger playing Jonathan Winters, will stoop to anything-we hope. His smorgasbord of the ridiculous is delightfully bereft of redeeming social value. Bad British drama is unbearable; bad British comedy can be sublime. CAPTION: Picture, Benny Hill